Download The Mid-term Results of Ventricular Containment (ACORN WRAP

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Article
The Mid-term Results of Ventricular Containment
(ACORN WRAP) for End-stage Ischemic Cardiomyopathy
Jai S. Raman, MBBS, MMed, FRACS, Mitsumasa Hata, MD, PhD, Meg Storer, BN (Hons),
John M. Power, BrSe, PhD, Brian F. Buxton, MB, MS, FRACS, Clif Alferness, BSEE,
and David Hare, MBBS, DPM, FRACP
The Acorn Cardiac Support Device (ACSD) is a device designed to treat heart failure by
containing the heart to prevent further dilation. Six patients with symptomatic heart failure due to ischemic cardiomyopathy were treated surgically with the ACSD. All patients
simultaneously underwent coronary artery bypass grafting (CABG). Ventricular reconstruction was also performed in 5 of the 6 patients. We followed up the patients for 12 months
postoperatively, monitoring the left ventricular ejection fraction (LVEF), left ventricular
end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), mitral
regurgitation, and the New York Heart Association (NYHA) classification. Both the LVEDD
and LVESD were significantly improved one month postoperatively (from 63.2 to 50.6 mm,
p=0.004, and from 51.6 to 39.5 mm, p=0.025, respectively). These dimensions did not change
significantly over the next 11 months. The NYHA functional class improved significantly
from a mean of 3 to 1.4 at 12 months (p=0.012). Mitral regurgitation improved from a mean
of 2.7 preoperatively to 1.4 at 12 months and the average LVEF also improved from 27%
preoperatively to 35.9% at 12 months after surgery. However these latter two results were
not statistically significant. There were no late deaths and no readmissions for heart failure.
Repeat coronary angiography at 6 months revealed patent grafts in all patients. The midterm results of the ACSD for patients with symptomatic heart failure suggest that ventricular containment may be useful for preventing further cardiac dilation in patients with ischemic cardiomyopathy. Randomized, long-term studies are needed to assess the efficacy
and possible role of the ASCD in the future management of heart failure. (Ann Thorac
Cardiovasc Surg 2001; 7: 278–81)
Key words: heart failure, ventricular containment, ventricular remodeling
Introduction
Heart transplantation is an accepted therapy for end-stage
heart failure in patients in whom medical therapy is not
effective in reaching therapeutic goals.1) However, it is
From the Department of Cardiac Surgery, Austin & Repatriation
Medical Centre, University of Melbourne, Melbourne, Australia
Received January 25, 2001; accepted for publication May 23,
2001.
Correspondence to Jai S. Raman, FRACS: Department of Cardiac Surgery, Austin & Repatriation Medical Centre, Austin Campus, Studley Road, Heidelberg, Vic 3084, Australia.
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limited by donor organ shortages, selection criteria, cost,
and limited prospects for long-term survival.2) Recently,
some promising results have been reported using left
ventricular reduction surgery and endoventricular circular patch plasty for end-stage cardiomyopathy.3,4) However, a recent study has shown that many of the patients
who undergo left ventricular reduction surgery still eventually require a heart transplant.5) We previously reported
the efficacy of geometric end-ventricular repair and the
early results of using ventricular containment to treat endstage heart failure.6,7) In this article, we report the midterm results of ventricular containment for symptomatic
heart failure due to ischemic cardiomyopathy.
Ann Thorac Cardiovasc Surg Vol. 7, No. 5 (2001)
Ventricular Containment for Ischemic Cardiomyopathy
Fig. 1. Schematic drawing of Acorn cardiac support device
(ASCD).
The ASCD is placed around the ventricles and anchored along
the atrioventricular groove posteriorly.
Patients and Methods
The Acorn cardiac support device (ACSD; Acorn Cardiovascular, St. Paul, MN) is a proprietary device designed to treat heart failure (HF) by constraining the heart
to prevent further dilation. It is constructed using a knitted polyester fabric similar to material found in vascular
grafts and is designed to optimize circumferential support while minimizing fibrosis.
From July 1999 to October 2000, 6 patients with symptomatic heart failure due to ischemic cardiomyopathy
who were undergoing coronary artery bypass grafting
(CABG) were also surgically treated with an ACSD. Informed consent was obtained from each patient and the
study was approved by the Austin & Repatriation Medical Centre Ethics Committee. The group consisted of 5
males and 1 female with a mean age of 64.7±7.1 years.
Five patients had additional ventricular geometric reconstruction of a large myocardial scar, a method which we
have reported previously.6) Patients were enrolled in this
series based on a combination of entry criteria, namely:
a left ventricular ejection fraction (LVEF) of less than
35% on radionuclide ventriculogram (RNVG); symptomatic heart failure; left ventricular end-diastolic dimensions (LVEDD) of more than 30 mm/m2 body surface
area; and coronary artery disease amenable to CABG.
Patients that required emergent or urgent surgical intervention were excluded. Other exclusions were repeat operations, major malignancy, or significant renal impair-
Ann Thorac Cardiovasc Surg Vol. 7, No. 5 (2001)
ment with a serum creatinine concentration of greater
than 160 mmol/L.
Before the patient was connected to cardiopulmonary
bypass (CPB), the circumference of the base of the ventricles was measured along with the apex to base length.
The ACSD comes in 5 sizes and the size of the mesh is
elected based on the pre-CPB measurement. Any large
aneurismal or akinetic left ventricular scar was then excised and the underlying ventricle reconstructed using
the geometric endoventricular repair technique. The
ACSD was then selected, placed around the ventricles
and anchored along the atrioventricular groove posteriorly (Fig. 1). Both ante and retrograde warm blood cardioplegia were concomitantly employed for myocardial
protection. The distal anastomoses were then constructed
with small windows created in the mesh to allow suturing. The edges of the windows were sutured down to the
epicardium to prevent encroachment of the anastomoses
or grafts. The cross-clamp was removed and the patient
weaned off CPB. At this stage, with the filling pressures
similar to those before CPB, excess mesh was excised
anteriorly from apex to base. The cut edges of the mesh
were then approximated with 4-0 polypropylene sutures
in such a way that the ACDS covered the ventricles in a
snug fashion. Implantation and tailoring of the mesh took
approximately 25 minutes.
We followed up the patients for 1, 6, and 12 months
postoperatively, monitoring the LVEF with RNVG,
LVEDD, left ventricular end-systolic diameter (LVESD),
mitral regurgitation (MR) with echocardiography, and the
New York Heart Association (NYHA) classification.
Coronary angiography was carried out 6 months after
the operation.
Statistical analysis was made by ANOVA using
Scheffe’s method. Significance was defined as a p value
of less than 0.05. The Mann-Whitney U test was also
used to compare abnormally distributed data.
Results
The average number of grafts was 3.5±1.0 with a range
of 2 to 5. There were no early deaths. One patient had a
septic episode postoperatively and another had their sternum re-explored on the ninth postoperative day for a suspected wound infection. One patient required intra aortic balloon pumping for 2 days postoperatively. There
were no late deaths and no readmissions for heart failure. The average LVEF improved from 27 % preoperatively to 35.9 % at 12 months postoperatively. However,
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Raman et al.
Fig. 2. Left ventricular ejection fraction (LVEF; %).
Average LVEF was improved from 27% preoperatively to 34.3%
in postoperative 12 months. No significant difference. POM6:
6 months postoperatively, POM12: 12 months postoperatively.
this was not statistically significant (Fig. 2). Both the
LVEDD and LVESD were significantly improved 1
month after surgery (from 63.2 to 50.6 mm, p=0.004,
and from 51.6 to 39.5 mm, p=0.025, respectively). However, there was no further improvement over the next 11
months (Fig. 3). The MR also improved from a mean of
2.7 preoperatively to 1.4 at 12 months postoperatively.
However, this was not statistically significant. All patients were in the NYHA class I or II at the time of review (the mean duration of follow-up was 465 days with
a range from 60 to 605 days). The NYHA status significantly improved from 3.2 to 1.4 in 12 months (p=0.012).
Repeat coronary angiography at 6 months revealed patent
grafts in all patients.
Discussion
In spite of a symptomatic improvement, progression of
heart failure has been demonstrated in trials among patients receiving the best currently available drug therapy.1)
ACSD is a newly developed device to avoid the deleterious effects of heart failure, in particular the phenomenon
of ventricular remodeling. Ventricular containment with
a modified polyester mesh was first performed as an adjunct to CABG on the 21st April 1999, on a patient with
symptomatic heart failure due to ischemic heart disease.7)
The ventricular containment device is intended to limit
the dilation of the heart that occurs with heart failure. It
may also reduce MR resulting from dilation of the left
ventricle. In this series, the etiology of MR was presumably from mild dilatation of the cardiac base and hence
the mitral annulus. There was no instance of severe MR.
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Fig. 3. Left ventricular end-diastolic (LVEDD; mm) and endsystolic dimension (LVESD; mm).
Both of them were significantly improved postoperatively at 1
month. Since then, they have not changed for postoperative 12
months. POM1: 1 month postoperatively.
No specific mitral valve intervention was performed. The
MR presumably decreased partly due to stabilization of
the cardiac base. The ACSD is a permanent implant that
has been successful in preventing the continual dilation
of the left ventricle in two heart failure animal models.8)
Pervaiz and colleagues9) also reported in an animal model
that the ACSD showed the effects of ameliorating myocyte hypertrophy and attenuating interstitial fibrosis. In
our patients, LVEF, measured by a gated blood pool scan
using RNVG, improved from 27.0% preoperatively to
35.9% 12 months postoperatively, but did not reach statistical significance because of the small number of patients. However, both LVEDD and LVESD were significantly decreased in the early postoperative phase and
these effects were maintained in the 12 months after surgery. Patients’ symptoms were also significantly improved in terms of the NYHA functional class. The ventricular containment seemed to prevent the development
of ventricular remodeling in the medium term.
Recent studies have suggested that increased left ventricular size is a risk factor for perioperative mortality in
patients with low LVEF undergoing bypass surgery.10)
We previously presented a new method of geometric left
ventricular reconstruction as representing a more physiologically effective repair.6) Suma and colleagues also
reported that surgical restoration produced a better outcome than CABG alone.4) The goal of left ventricular
reconstruction is to reshape and reorganize the ventricle,
while reducing the volume. However, the long-term results of this technique are not yet known. Another im-
Ann Thorac Cardiovasc Surg Vol. 7, No. 5 (2001)
Ventricular Containment for Ischemic Cardiomyopathy
portant problem is the return of intractable heart failure
due to progressive dilatation. Though the reduced ventricular geometric dimensions may be sustained for up
to 12 months, pump function begins to deteriorate after
6 months. The discrepancy between geometry and
sustainability of mechanical function is attributed to the
fact that mass reduction causes changes in diastolic compliance.11) In our patients, the echoes were reviewed and
reported by the core lab at Mayo Clinic with no evidence
of diastolic dysfunction or pericardial constriction. From
a therapeutic standpoint, then, the surgical procedure targeted to inhibiting or reversing some aspects of this remodeling process of heart failure appears to be a particularly attractive one. We consider that the goal of the
surgical reversal of remodeling is to reshape the LV from
a globular to an elliptical shape without critically reducing the cavity volume and allowing further dilation. In
this respect, ventricular containment with a customized
polyester mesh such as that represented by the ACSD
seems like a logical surgical approach to heart failure.
Conclusions
The mid-term results of ventricular containment with a
customized polyester cardiac support device for patients
with symptomatic heart failure are promising. This device may be useful in preventing the further development
of ventricular remodeling in ischemic cardiomyopathy.
However, randomized, long-term studies are needed to
further assess the efficacy of ventricular containment and
to define its possible future role in the surgical management of heart failure.
Ann Thorac Cardiovasc Surg Vol. 7, No. 5 (2001)
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